Composite structures, such as wind turbine blades, comprise a plurality of layers of sheets made of fibres embedded in a resin. These sheets are traditionally cut from an endless sheet material and stacked in layers on each other to form a composite structure. The composite structure is then consolidated by removal of any air trapped between the layers of the structure, usually by applying a vacuum. During this consolidation procedure, additional resin may be introduced to, or infused in, the structure to fill any voids therein to strengthen the structure.
WO 2006/082479 relates to an endless cured composite sheet material for manufacturing a wind turbine blade shell member. The cured sheet material is cut into elements, which elements are stacked overlapping in a mould, wherein resin is introduced between the elements and cured to bind the elements to each other. The elements may have a surface texture which facilitates introduction of resin between adjacent elements.
EP 1 754 589 relates to a continuous cured laminate, which, during manufacture, is provided with channels for a curable material to move in, during an infusion process, between layers of the continuous laminate arranged in a stack.
US 2006/0175731 relates to a method of preparing a more reliable connection between two adjacent composite members for the production of wind turbine blades and spars for such blades. The method involves the use of a gas-removal layer, which allows for gas transport in a number of overall directions in a plane of the gas-removal layer. The gas-removal layer comprises a resin and is deformed during consolidation to form a connection substantially free of trapped gas voids.
These documents have the objective of constructing larger structures from stacked sheets. Such construction has a problem with air being trapped within the structure, causing weak zones reducing the overall strength of the structure. The present invention provides an improved technique of facilitating the removal of such trapped air.